So I guess those signals are in GHz range, right ? If they are so, your task is a little bit difficult because Phases are very important here and it's not possible to expect 100% performance with passive circuits such as Balun. Because they have Phase Error and as well as Amplitude Error.Hi,
It has to be passive, the pulsewidth is 500ps with the rising/falling edge 80-90ps. No op-amp will do that so it has to be some rf technique
Can you define the function more clearly rather than what you did?Hi,
I have a question about the best way to combine to short pulses with small amplitude to obtain a monocycle pulse.
I am using a fast CML Comparator to generate short pulses (roughly 0.5 - 1nS) which i differentiate both complementary outputs to remove the DC part the and the positive edge i delay (using TL) by the pulse width in order to offset them. What is are some of the ways to recombine these pulses as I need to feed them into a MMIC amplifier?
Amplitude of these pulses is relatively small at this stage around 200-300mV
Many Thanks
I take the output of a fast CML Comparator ( ADCMP572) and I get a 200mV pulse in 50Ohm load. Width FWHM of 500ps. Yes it is a repeating monocycle with a frequency of 100MHz. Rise fall times already mentioned around 60-80pS and since its CML the source really is current steering logic.Can you define the function more clearly rather than what you did?
Vin = 200~300 mVpp , Vdc offset= ?
PW50 = {min, typ, max or Nom. +/-%} (50% amplitude width)
Purpose: 1-shot 750 ps +/- 250 ( i.e. monocycle Is that like a unicycle ?Does it repeat ? What's it for?
trailing or leading edge ??
Latency = ??
Rise/Fall time = ??
Voltage or current source?
Output: CML ?? or single or differential? ? or define logic levels like 1V @ 50 Ohms or
Supplies avail??
Operating ambient temp range?
Fairchild was the first to make sub-ns ECL one-shots in the 70's when I started work.
Today 1 picosecond 1-shots are used in lasers.
My understanding was baluns convert signals that are 180 degree out of phase into SE. Here I just need to superimpose the two pulses into the same amplifier inputSo I guess those signals are in GHz range, right ? If they are so, your task is a little bit difficult because Phases are very important here and it's not possible to expect 100% performance with passive circuits such as Balun. Because they have Phase Error and as well as Amplitude Error.
You can realize such circuit with discrete component using with RF/Microwave Transistors but this needs highly Design Experiences.
I believe a L-C Balun will serve you better. But it should be carefully designed and the layout must be perfect. Be careful about the components that you'll use.
OK, understood. So you will work in Time Domain.My understanding was baluns convert signals that are 180 degree out of phase into SE. Here I just need to superimpose the two pulses into the same amplifier input
Hi,Wikiwand - Balun
A balun is an electrical device that allows balanced and unbalanced lines to be interfaced without disturbing the impedance arrangement of either line. A balun can take many forms and may include devices that also transform impedances but need not do so. Sometimes, in the case of transformer...www.wikiwand.com
This is what I understand.
Combine two consecutive 100 MHz rep rate pulses 200 mV (0-pk) x 500 ps @ 100 mV with DC offset
- to remove the leading edge so you can see the difference in the trailing edge of consecutive pulses.
- you have differential outputs are passive differentiated to remove DC (and leading edge ?)
Other important variables may include;
DL path loss, amplitude variation, PW variation, jitter, amplitude matching, sync error one leading edge, pulse jitter due to AM, spectral density of source and essential BW.
You have a differential Comparator so you can sum analog signals by the difference of of complementary signals one being delayed -inverted but you want to cancel the lead edge so delayd non-inverted.
You can use a splitter and balun in either direction. The Balun raises the CM impedance much higher than the Zo so the differential out is more balanced or you can convert single-ended to differential and visa versa.
So you can combine using Differential inputs or use Balun or use a 3 dB splitter as a combiner. rated from say 10% to 10x
We once used cascaded LC all pass delay lines in 2 ns increments to measure window margin instead of eye pattern for 10 MHz data in the 80's in an automated test set.
Maybe you can draw some signals in a block diagram to show the measurement you want out with resolution & tolerances with the above variables that matter..
I need single ended for the MMIC amplifier which cannot accept differential.What is your rise time spec?
0.35/ 2 GHz has half power at 175 ps 10~90% risetime.
At these speeds you ought to be using differential to avoid CM or unbalanced threshold errors.
This is exactly from my initial post:i am not following your circuit.
if you differentiate a positive going square wave leading edge, you get a positive going spike. If you differentiate the negative going square wave leading edge, you get a negative going spike. If you delay the first and recombine the two you get two spikes exactly canceling each other out! i.e. an all-stop filter.
maybe explain WHAT your system is intended to do, rather than immediately talk about the hardware implementation.....
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